File:A Turing Bombe, Bletchley Park - geograph.org.uk - 1590991.jpg

English: A Turing Bombe, Bletchley Park. The BOMBE was named after and inspired by a device that had been designed in 1938 by the cryptologist Marian Rejewski of the Polish Cipher Bureau, who revealed their deciphering technique to the British just prior to WWII. Unlike COLOSSUS 1590854, the bombe was not a programmable computer, but an electromechanical machine designed to assist British cryptologists to break into German Enigma-machine-enciphered wireless traffic. Designed by Alan Turing 1591025, with an important refinement suggested by Gordon Welchman, the bombe made its first appearance during 1940 and refinements followed, particularly in the later American version.

A standard German Enigma employed, at any one time, a set of three rotors (in the German Navy, from early 1942, four rotors), each of which could be set in any of 26 positions. The bombe tried each possible rotor position and applied a test. The test eliminated thousands of positions of the rotors; the few potential solutions were then examined by hand. In order to use a bombe, a cryptanalyst first had to produce a "crib" - a section of ciphertext for which he could guess the corresponding plaintext. During the war, bombes were built by the British Tabulating Machine Company at Letchworth and by May 1945 there were 211 operational machines requiring nearly 2,000 staff to run. After the war some fifty bombes were retained in Britain for intelligence work, while the rest were destroyed.

A team led by John Harper conducted a 13-year project to reconstruct a working bombe, which was completed in 2007 and can be seen at the Bletchley Park Museum. For more information about the BOMBE, see . . . . http://en.wikipedia.org/wiki/Bombe

For other views of the bombe, see:

1590899; 1590986; 1590989; 1590992; 1590993; 1590996; 1590997;

1591001